you know the Flood right? cute little octopus things, crawling inside you, suddenly there's nasty tentacles sprouting from your limbs and chest...i love these space zombies (as one might put it)
so, Halo 3. Master Chief fired the Halo ring and killed the Flood off for good. right? WRONG!!!
let's go back to Halo 2.
on the second Halo ring, Installation 05, the flood broke out again. they manage to take over High Charity, the Covenant't Holy City.
Cortana stays on high charity to destroy it, with the flood, should the Halo ring fire...the ring does not fire, and thus high charity isn't destroyed, blah blah blah, ends up on the Ark in Halo 3
NOW. surely not all the flood went to the Ark. surely some of them stayed behind on the second ring, making themselves feel right at home.
so you see. Bungie left out a plot that i think should be accessed in the new reclaimer Trilogy. a Halo Ring completely taken over by the Flood. not just the ring. the planet the ring was orbiting around ((they do orbit, right?)) should be affected by the Flood as well. how? well, the Flood have a knack for reanimating space shuttles, surely their must of been a few crashed Covenant ships or dropships from both sides left on the ring, giving them the chance to travel to the planet. and not just for travelling to the planet, but is it possible they can use whatever ships that are left on the ring to form a small fleet, or even learn how to form their own organic ships if they haven't already.
and speaking of reanimating veichles, is it possible the Flood can reanimate robots...say, the sentinels for example.
in Halo 2, we encountered a new kind of sentinels...the big ones (for lack of proper word). now, wouldn't they be large enough for the Flood to reanimate? what kind of chaos could they cause with that? Giant, flying floods? or even the mysterious Flood juggernaut, an enemy that was dropped from Halo 2. i'd
like to go one on one with that ugly thing.
Finally, what kind of power can the Flood have when in control of an entire Halo Ring. could they modify it's weaponry systems? highly unlikely they'd fire the ring to infect the entire universe, but it's a thought.
so, put simple. Cortana didn't destroy the second Halo Ring, Flood take over said ring, travel to planet, take that over as well. now they got their own planet and a Halo Ring, Master Chief has to return here before the Flood create an army to infect all Human/Alien life as we know it.